1. Field of the Invention
The present invention relates to mats for bearing and supporting objects, especially for packaging purposes, comprising an air tight, flexible case which can be closed by a valve and which contains an appropriate filling material.
2. Description of Prior Art
In the known mats of this kind, the filling material consists preferably of a pre-expanded granules of polystyrene. In the known realization described in the U.S. Pat. No. 3,212,497, the granules are filled up in a textile bag. With such realization, there is the risk that the granules, especially when held vertically in pressureless condition, accumulate in the lower part of the bag while the upper part of the bag is empty of granules. When using this mat, the granules first have to be evened out before applying the vacuum. The DOS 2.018.605 reference describes a solution where the granules are captured in segments of the case (FIG. 5) in such a way that the air can be drawn out of the segments without any escape or exchange possible of the granules between the segments. The PCT/FR87/00115 suggests an embodiment of such a realization with segments where the granules are captured in padded or tube-shaped segments (FIGS. 5 and 8).
The problems of the known mats reside in a conflict of objectives. On one hand, a loose fill of granules as described in the U.S. Pat. No. 3,212,497 is desirable in as much as the granules are constantly mixed when the mat is pressureless. On the other hand, the uncontrolled accumulation of granules in one area of the mat in a pressureless condition is not desirable because of the enhanced handling of the mat. The capturing of the granules in segments or tubes has the disadvantage that certain areas and especially the central areas of the mat suffer a special mechanical stress and cannot regenerate sufficiently while pressureless, as there is no exchange of granules between the central and the marginal areas. So, especially with the embodiment described in PCT/FR87/00115, a sensible shrinkage of the granules takes place in the central segments or tubes after a relatively short time and, consequently, undesirable thin spots show up in the mat. These thin spots or areas cannot be evened out or smoothened for a reliable use of the mat. Another common disadvantage of the known mats resides in the fact that thin spots or areas are built along the separation lines of the segments or tubes. This, however, is very disadvantageous for the goods to be packed as the apparent thickness of the mat, in fact, does not exist. This defect cannot be detected or seen from the outside.